Measuring instrument



1933- i T. R. HARRISON ET AL 2,132,617

MEASURING INSTRUMENT Original Filed June 25, 1931 5 Sheets-Sheet 1 FIGI.

IN V EN TOR. THOMAS R. HARRISON, ERNEST H. GRAUEL,

BY 8 JOHN E. KESSLER Oct- 11, 193 T. R. HARRISON ET AL 2,132,617

I MEASURING INSTRUMENT Original Filed June 25, 1951 3 Shets-Sheet 2FIGA.

IN VEN TOR. THOMAS R. HARRISON, ERNEST H. GRAUEL,

&JOHN E. KESSL$ E ATTORNEY Oct. 11, 1938. T. R. HARRISON ET AL 2,132,617

MEASURING INSTRUMENT Original Filed- June 23, 1951 s Sheets-Sheet s Nmuuunn HA p IN VEN TOR. THOMAS R. HARRISON, v ERNEST H.6RAUEL, (0 BY 8JOHN E. KESSL R QM? m ETTORNEY Patented Oct. 11, 1938 I 2,132,617;PATENT OFFICE Y 2,132,617 MEASURING INSTRUMENT .Tliomas R. Harrison,Wyncote, Ernest H. Grauel,.

Perkasie, and John E. Kessler, Gettysburg, Pa., assignors to The BrownInstrument Company, Philadelphia, Pa., a corporation of PennsylvaniaOriginal application June 23, 1931, Serial No.

546,290. Divided and this application Novemher 4, 1936, Serial No.109,124

4 Claims.

The general object of the present invention is to provide improvementsin galvanometer construction, to the ends of simplifying and reducingcost of manufacture, and of providing a desirably simple and effectivegalvanometer assembly, having a maximum accessibility for adjustment andservicing operations and a minimum of structural features subject tofailure in operation.

While a galvanometer embodying our improvements is adapted for use withadvantage in various relations and for various purposes, it may be usedwith a special advantage in a potentiometer measuringinstrument which,because cf'its operating characteristics and the relatively large numberof operating parts which it comprises, is

relatively bulky, and imposes special spatial restrictions on the formand disposition of the galvanometer included in the instrument, andmakes it especially important that the. galvanometer should beconstructed and rranged so that its relatively delicate parts may iiereadily separated from the remainder of the instrument, when necessaryfor repair, adjustment, or replacement operations.

Special objects and advantages of the invention are made apparent in thefollowing detailed description of an embodiment of the inventionillustrated in the accompanying drawings, of which:- D

Fig. 1 is a sectional plan, withparts broken away and removed, ofaportion of a potentiometer instrument including a galvanometer con-:fructed in accordance with the present inven- Fig. 2 is a frontelevation, with parts broken away and in section, of a portion of theinstrument shown in Fig, 1;

Fig. 3 is a plan view of the galvanometer enclosure partly broken awayand in section to illustrate the galvanometer zero adjustmentmechanism';

Fig. 4 is a perspective view of the galvanometer assembly, with theparts separated for clearance; Fig. 4a is an enlarged reproduction of aportion of Fig. 4 illustrating the galvanometer pointer and coilstructure;

Fig. 4b is a section on the line 4b4b of Fig. 4a;

Fig. 5 is a front elevation of the galvanometer unit;

Fig. 6 is a rear elevation of the galvanometer unit; andN Fig. 7 is aperspective view of a molding forming an element of the galvanometerassembly.

In the embodiment and use of our invention illustrated in the drawings,the galvanometer forms a part of a potentiometer instrument disclosed inour prior application, Serial No. 546,290, filed June 23, 1931, of whichthe present application is a division. In said instrument, the bulk ofthe instrument mechanism is mounted on aframe instrument, thegalvanometer is mounted in a recess 64 formed in the frame 41, and openat its upper end and at its rear side, though in the normal operatingcondition of the instrument, the galvanometer is surrounded by the wallsof an' enclosure formed in part by the member 41,.

and in part by removable cover parts I24, I21, and I26, hereinafterdescribed.

The galvanometerassembly includes a plate 66, detachablysecured againstthe ijront vertical wall of the recess 64 and forming the member throughwhich the galvanometer assembly is normally secured to the frame 41. a

The plate 66 is provided with an aperture 61 through which a screw 66extends to secure the plate 66 to the frame 41. Projections 68 are,provided on that surface of the plate 66 adjacent the surface of theinstrument frame and fit into recesses in the frame 41, so as properlyto align plate 66 when secured in place. Plate 66 is provided with pins69 which extend into recesses (not shown) in pole pieces 60 of thegalvanometer horse shoe magnet 64, thereby properly positioning the polepieces. The pole pieces 60 are provided with threaded recesses 6| intowhich bolts 62 are screwed, the bolts passing through apertures 63 inthe magnet 64 and securing the magnet 64 to the pole pieces 60. A hook66 extends over .the magnet 64, and through an aperture 66 in plate 66,and the magnet 64 is clamped to the plate 66 by the nut 61 applied tothe threaded end of the hook 65. Studs 68 extend through apertures 69 inplate 56 and are threaded into pole pieces 60 to secure the pole piecesto the plate 56, the pole piecesbeing provided with apertures IIIthrough which the ends of studs 68 extend.

The ends of studs 66 are arranged to pass through apertures II in aBakelite molding I2. The studs 66 are provided with recesses I3, adaptedto accommodate notches I4 in clamping bar I2 are in assembled relation,the bar I6, when turned into clamping position with respect to studs 66,secures the Bakelite molding to the magnet system. The bar I6 is mountedon the Bakelite molding 12 for rotation by bolt I6. The

bolt I6 extends through passage II in core l6 adapted to fit within Qthegalvanometer coil and provide a uniform electro-magnetic field in whichthe galvanometer coil may move.

The Bakelite molding is provided with a projection I9 having a faceshaped to receive and support the core I8 and the body of the molding I2is provided with aperture 8| through which the bolt I6 passes. Suitablesecuring means, such as washer and nut 82, are threaded on the end ofthe bolt IE to secure the core I8 in place. The bolt 16 is provided witha recessed projection 83 over which the aperture 84 of the bar I5 fitsand which accommodates a cotter 85 to secure the bar I5 into position onthe end of the bolt I6.

The molding I2 has upper and lower extensions 86 provided with shoulders81 and ways 88 respectively adapted to receive and guidably supportupper and lower fittings 89 for motion longitudinally of the extensions86. Each fitting 89 is provided with an offset 90 which contacts withand rides along the faces of the shoulders 81. The face or body portion9I of each fitting'89, fits into the way 88 of the molding. The offset90 of each fitting 89, cooperating with shoulders 81, and thecorresponding face 9I, cooperating with way 88, support the fitting 89against lateral movement with respect to the corresponding extension 86.Each fitting 89 is provided with a lug 92 having a threaded aperture 93into which is threaded a thumb screw 94. The shaft of the thumb screw 94extends through a corresponding aperture 95 in the Bakelite molding I2.The end of each thumb screw 94 is provided with a recess into which fitsa cotter 96 for securing the thumb screw against longitudinal movementwith respect to the molding I2, and for limiting the movement of thecorresponding fitting 09 along longitudinally of the corresponding thumbscrew 94. Rotation of each thumb screw 94 shifts the correspondingfitting 89longitudina1ly of the extension 86. Each fitting 89 isprovided with a threaded aperture 91 to receive a screw 98 passingthrough a clip 99, having ears I00 which ride on the face IOI of thecorresponding extension 86. The clips 99, when secured in place by thescrews 98, afford additional support against lat eral movement for thefittings 89.

Each clip 99 and screw 98 serve an additional function in that they formmeans used in connecting the galvanometer leads, or terminal conductors,99' and 99'.'., to the galvanometer coil or winding, as shown in Figs. 2and 6. As shown in Fig. 6, an electrical connection is made between eachclip 99 and the galvanometer suspension by a corresponding conductor I02secured to the clip 99 as by soldering, or any other suitable means, andsecured to the corresponding spring I03, to which the correspondinggalvanometer suspension part is connected, by a soldered or othersuitable joint between the conductor I02 and a bent lug portion I04 ofspring I03.

Each spring I03 is provided with an aperture I05 which fits over aprojection *I06 carried by arm I01 pivotally mounted as by means of pinI08 on the lug portion I09 of the corresponding fitting 89. Each springI03 is secured in place upon the corresponding arm I01 by turning overthe projection I06, or in any other suitable manner. The pivotalmounting of each arm I0'I on the corresponding lug I09, provides foradjustment of the galvanometer suspension about its axis in order toproperly position the galvanometer suspension with respect to the zeropoint as determined by the other parts of the instrument with which thegalvanometer suspension is associated. In order that movement of eacharm I0'I about'its pivot I08 may provide only rotational adjustmentof-the galvanometer suspension, each spring I03 is formed with, anextension IIO to which a bushing I I I is secured in such position as tobe in axial alignment with the pivots I08 when the spring I03 is securedto its arm 'I0'I by projection I06from the latter. may be secured to thecorresponding spring I03 by welding or in any other suitable manner.Each bushing III receives a ferrule II2 which is secured thereto bymeans of screws passing through the bushing or in any suitable manner. Asuspension wire or strip H3 is secured to each ferrule I I2 as bysoldering. A ferrule at the coil adjacent ends of two suspension wiresH3 is secured to upper and lower bosses II4 fastened as by welding tosheet metal clips II5 which are bent around the top and bottom portionsof the galvanometer coil II5a to 'rigidly connect the galvanometer coiland bosses. One of said clips I I5, the upper one as shown, is providedwith an integral projection having at its end an uprising edge H6. Thesame clip H5 is provided with a projection II'I extending in theopposite direction from the first mentioned projection, to which issecured, as by welding, a leaf spring II8 forming an extension of thepointer II9 of the galvanometer. The spring H8 is provided with apertureI28 through which boss II4 extends. The spring H8 is provided with aridge or like edge forming surface I2I adapted to cross and rest uponthe edge H6. The point of contact between edge H6 and ridge I2I affordsa single point of hearing about which the pointer II9 may be movedslightly during the hereinafter mentioned operation of the mechanism forgauging the position of the galvanometer, thus providing a single pointof support between the galvanometer pointer and edge 6, whereby wabblingof the pointer and distortion of the suspension sys- Each bushing IIItem due to force acting on the pointer, is prevented, which isespecially important because the gauging operation tends to set thepointer into vibration at the time of releasing the pointer. The contactbetween edges H6 and I'll damps the pointer oscillations and quicklybrings the pointer to rest. The clip I I5 to which the pointer H9 issecured, is provided with a threaded rod I2'I' projecting laterally ofthe coil in line with the pointer which carries the nut I22 threadedthereon for adjustment to balance the weight of the pointer II9.

As will be observed in Figs. 5 and 6, the parts shown in displacedrelation in Fig. 4, when assembled, are so arranged that thegalvanometer coil II5a extends about the core 18 and is situated betweenthe poles 60 of the magnet, the whole system comprising the galvanometersuspension, core, magnet, and poles being clamped together by bolts 68and cooperating parts. The molding I2, as shown in Fig. '7, is providedwith four troughlike depressions I23, so positioned that when themovable system of the galvanometer is being assembled, the bosses II4 onthe galvanometer coil supporting clips, rest in a pair of the recessesI23, and the ferrules II2 distant from the galvanometer coil rest in theother pair oh'ecesses I23. Recesses I23 provide convenient supports forthe parts mentioned to facilitate the plicity of construction, affordingfacility of man- 51 in plate 56. The unit is arranged for facility ininspection, dismantling, service and repair.

The recess 54 in the instrument frame or arm 41 on which thegalvanometer unit is mounted, is provided with a rear cover I24 (seeFigs. 1, 2, and 3), which is adapted to fit onto the walls of therecessed portion of the frame by spring action, and can be removedmanually when the instrument frame is swung out of the casing, makingthe back of the frame available. A cap I 21 (Figs. 1, 2, and 3) closesthe top of the recess and rests upon the top edge I26 of the recess 54,closes the top of the recess space proper, and forms the top and sidewalls ofan upper horizontal front extension of that space. The extensionspace I25 receives the galvanometer pointer H9 and cooperating pointerposition gauging mechanism. A front cover part I28 forms the front ofthe cap I21 and is provided with a window through which the galvanometerpointer and the pointer gauging mechanism may be viewed.

As shown in Fig. 3, the cap I21 rotatably carries in apertures formedtherein, a shaft I29 which extends through the front of the cover I28,its exposed end being provided with a kerf. Shaft I29 carries on itsother end a gear I3I meshing with gear I32, the axle of which isjournaled in the bushing I33 molded into the material of the cap. Whenthe galvanometer unit is mounted in position upon the instrument frame,and when the cap and associated parts are mounted in position, the axleof gear I32 is in axial alignment with pivots I08 and the galvanometersuspension. The spring I03 carried upon the upper fitting 89 by an armI01 rotatable about pivot I08, is provided with an upward extension I34having a'ridge I35 formed therein, which, as shown in Figs. 2 and 3, isadapted to extend between teeth of the gear I32, so that rotation ofgear I32 bv manually effected rotation of, shaft I29, will transmitangular motion to the upper spring I03 and galvanometer suspensionconnected thereto, about the axis of the suspension. Such adjustment ofthe galvanometer suspension about its axis is provided to set thepointer to the zero positionrelative to the other parts of theinstrument, when no current is flowing through the galvanometer. Theconstruction of the zero adjusting means of the galvanometer is simple,trouble free, easy to make, conveniently arranged for operation on theinstrument, and readily assembled and available for servicing.

The previously mentioned pointer positiongauging mechanism, shown inpart in Fig. 1, comprises parts co-acting periodically to clamp thegalvanometer pointer II9 against deflection and acting through an armI13, carried by a rod or shaft I14, to adjust the latter into an angularposition depending upon the deflective position of the pointer I I9 atthe time. The construction and mode of operation of the gaugingmechanism need not be further referred to herein as they form no part ofthe invention claimed herein, and are fully disclosed in our parentapplication Serial Number 546,290. It is to be noted, however, that thefeatures of galvanometer construction and arrangement claimed herein arewell adapted for the ready and effective association with thegalvanometer, of a suitable gauging mechanism, and that the galvanometerpointer and the means for supporting the galvanometer coil, are welladapted to withstand the shock' and vibration resulting from theclamping and release of the galvanometer pointer in the gaugingoperation. The portions of the member 41 adjacent the recess 54 andextension space I25, and the cover parts I24, I21 and I28, form a closedhousing for the galvanometer unit and 'associatedgauging mechanism unit,affording ready and complete access to those units together withprotection from external influences.

While we have herein illustrated and described a preferred specificembodiment of the invention herein claimed, variation may be made indetails of construction and arrangement of the embodiment illustratedwithout departing from the spirit and scope of the invention as definedin the followingv claims.

Having now described our invention, what we claim as new and desire tosecure by Letters Patent is:

1. In a galvanometer of the dArsonval type, the combination with thegalvanometer coil and suspension system, of a molding of insulatingmaterial, means for mounting the system on the molding including springsfor tensioning the system and means for adjustment of the systemrelative to the molding in one direction, said first mentioned means andmolding being relatively adjustable for adjustment of the systemrelative to the molding in a second direction.

2. In a galvanometer of the dArsonval type, the combination with agalvanometer coil and suspension system, of a molding of insulatingmaterial, and means for mounting the system on said molding includingsprings for tensioning said system and including means for adjustment'of the angular position of the system relative to the molding, saidfirst mentioned means and molding being relatively adjustable to varythe positions of said springs relative to said mold-. ing and relativeto each other.

3. In a galvanometer, a movable galvanometer coil,,a clip secured tosaid coil, a suspension element connected to said clip, a leaf springextending from said clip in a lateral direction relative to the coil, apointer secured to the leaf spring, and a supporting member on said clipand having an edge extending transversely to the direction of the planeof flexure of the leaf spring, said spring being provided with a narrowsurface arranged to extend transversely of,

- and rest on, said edge.

the frame.

THOMAS R. HARRISON. ERNEST H. GRAUEL. JOHN E. KESSLER.

